Magnetic recording in law enforcement is used in interviews with suspects, as a memory aide for investigators both at crime scenes and witness interviews, for intelligence gathering and secret meetings, and for recording of both communications and special operations. Poor acoustical design of police stations and inadequately trained operators contribute to the inability to obtain high quality tape recording. Moreover, the increased use of tape-recorded evidence generated outside police stations has increased problems of authentication, continuity, safe storage, and the verification of the original tape recorder. To overcome these problems, architects are asked to consider the accoustical requirements in the design of future police stations, and design modifications to existing ones. Efforts to eliminate various forms of sound interference by user education, microphone placement, and soft rubber microphone shields have been moderately successful. When the validity of a tape recording is questioned, a program of subjective and objective analysis is undertaken. Five criminal cases in which tape-recorded evidence played a significant role are discussed.